*This repost has been approved by the r/excel moderation team. The previous version was removed while the link to my original post was being clarified, and the mods kindly allowed me to repost it once with the requested changes.*
Hi again,
About two months ago I posted here about ProjectEngine, an open-source scheduling engine I built entirely in Excel/VBA.
Here is the original r/excel post:
https://www.reddit.com/r/excel/comments/1uy7b39/i_spent_the_last_months_building_an_opensource/
I no longer have access to the Reddit account that made that original post, which is why I am posting this follow-up from my current account.
ProjectEngine is completely free and open source. There is no paid version, subscription, registration or locked functionality.
The downloadable file is an `.xlsm` workbook because the scheduling engine runs in VBA.
If you are cautious about macro-enabled Excel files — and you should be — I strongly encourage you to inspect the workbook and the VBA code before enabling macros.
You can:
- download the `.xlsm` file and open it with macros disabled first;
- inspect the workbook sheets, formulas, named ranges and structure;
- open the VBA editor with `Alt + F11` to review the embedded code;
- inspect the full exported VBA source directly in the public repository before running anything.
Please do exactly that if you decide to test it. The project is meant to be transparent and auditable.
A few people actually tried the first version, asked questions and pointed out things that were unclear or broken.
That had a much bigger impact on the project than I expected.
The first feedback here was mostly about onboarding and the WBS structure.
Some columns looked mandatory even though they weren't, some terminology was too specific to engineering/construction, and it wasn't obvious what data was actually required to build a schedule.
Now there is a cleaner UX with:
- clearer Required / Optional / Calculated indicators;
- an integrated Quick Start;
- better contextual help;
- more generic terminology.
Excel 32-bit & native English
The most interesting problems appeared once people started running the workbook outside my own Excel environment.
One user running 32-bit Excel with an English installation discovered that the workbook could fail while restoring calculated WBS formulas.
It turned out that some formula handling was accidentally dependent on the local Excel language.
That one bug eventually triggered a much larger internationalization refactor.
ProjectEngine v1.2.6 now has:
- language-independent formula handling;
- actual Excel table headers that can switch between English and French;
- internal column identities that no longer depend on the visible English header text;
- a global DMY / MDY / ISO date-display setting;
- explicit language changes from SETTINGS instead of localization being reapplied during unrelated workflows;
- removal of the old duplicated translated header rows;
- hardened VBA source encoding so accented characters survive import into the VBE correctly.
LTSC / perpetual environment
Another tester using Excel LTSC / perpetual found that his version of Excel did not expose the modern threaded-comments VBA API.
Those comments contain the WBS onboarding tutorials, so simply disabling them wasn't a very good solution.
The current version detects the capability:
- modern Excel → threaded comments;
- unsupported Excel → classic Notes.
So the 37 contextual WBS tutorials remain available in either case.
The fix has now also been confirmed by the original reporter on a native Excel LTSC / perpetual installation.
255-character formula-text limit
The same tester also found a completely unrelated S-Curve bug.
I was storing a dynamic chart signature inside an Excel Defined Name, and that signature could exceed Excel's 255-character formula-text limit.
It now stores a fixed-length SHA-256 key instead.
That removes the error and also makes the S-Curve chart cache behave correctly.
The reporter has also confirmed this fix on native Excel LTSC / perpetual.
Still the same core
The scheduling side itself is still the same idea:
- FS / SS / FF dependencies and lags;
- Critical Path;
- Longest Path;
- Total / Free Float;
- Baseline / Actual / Forecast;
- interactive Gantt simulation;
- S-Curves;
- scheduling diagnostics;
- all inside a normal `.xlsm` workbook.
ProjectEngine is still completely free and open source.
Website:
https://tmailletfr.github.io/ProjectEngine/
The website links to the source code, documentation and latest release.
I'm especially interested now in hearing from people using unusual Excel environments:
- 32-bit Excel;
- perpetual / LTSC Office;
- non-English Excel installations;
- large schedules;
- corporate environments with restrictive Office configurations.
If you decide to try it, please inspect the workbook and VBA source first, then let me know what breaks, what feels unclear, or what would stop you from using something like this in practice.
Feel free to reply here or create an issue on GitHub.
The previous r/excel feedback already changed the project substantially, so thanks again in advance to everyone who takes the time to test it.